'When I learned of City's interest my heart was set on coming here and things have moved very quickly.

'I
have loved my time with Borussia Dortmund and I would like to thank the
club and the supporters for the five very happy years I spent there.

'They gave me a platform to play on and I became a better player because of the belief, patience and trust they showed in me.

'Now
I have a new challenge and that is to achieve great things with City.
The opportunity to work with a coach like Pep Guardiola is something I
am really looking forward to and I am flattered to be the first signing
the club has made this summer.

'I
can promise the City fans I will give everything to help us win titles
both in England and the Champions League. These are exciting times.

'I
have my best years ahead of me and I think we can achieve great things
together. I can’t wait to begin this new chapter in my career.'